Electron Configuration

Electron Configuration electron configuration is the distribution of electrons of an atom in atomic or molecular orbitals. For example, the electron configuration of the neon atom is 1s2 2s2 2p6.

The Quantum Mechanical Model based on quantum theory, which says matter also has properties associated with waves. This theory states it’s impossible to know the exact position of each electron at the same time. This is known as the Uncertainty Principle.

The Quantum Mechanical Model Each energy level contains a definite number of orbitals of specific types The different types being called subshells Each subshell contains a specific number of electrons

Quantum Mechanical Based on Probability This model determines where there is likely to be an electron. So, this model is based on probability (MATH!) rather than certainty.

Orbitals

Orbitals -Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found. (s, p, and d orbitals) -Bohr used orbits; Schrodinger used orbitals

Energy Level 1 s Orbital (1 orbital)

Energy Level 2 2 subshells: s and p s orbital (1 orbital) p subshell (3 orbitals)

Energy Level 3 3 subshells: s, p, and d s orbital (1 orbital) p subshell (3 orbitals) d subshell (5 orbitals)

Energy Level 4 4 subshells: s, p, d, and f s orbital (1 orbital) p subshell (3 orbitals) d subshell (5 orbitals) f subshell (7 orbitals)

The numbers and kinds of atomic orbitals depend on the energy sublevel.

The number of electrons allowed in each of the first four energy levels are shown here.

Electron Arrangement in Atoms If this rock were to tumble over, it would end up at a lower height. It would have less energy than before, but its position would be more stable. Electrons are more stable in lower energy levels

Electron Configuration Rules! Three rules the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms.

Aufbau Principle The electrons fill the lowest energy level first Each orbital can hold a maximum of two electrons If there are 2 or more vacant orbitals of the same energy level, each orbital accepts one electron before the orbitals in the subshell begin filling the second electron. (Hund’s rule) -this happens in the 3 p orbitals of the p subshell

Hund’s Rule Hund’s rule states that electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible.

this happens in the 3 p orbitals of the p subshell Hund’s Rule 3) If there are 2 or more vacant orbitals of the same energy level, each orbital accepts one electron before the orbitals in the subshell begin filling the second electron. (Hund’s rule) this happens in the 3 p orbitals of the p subshell

Aufbau Principal Simple Version According to the aufbau principle, electrons occupy the orbitals of lowest energy first. In the aufbau diagram below, each box represents an atomic orbital.

Pauli Exclusion Principle atomic orbital have at most two electrons. To occupy the same orbital, two electrons must have opposite spins; that is, the electron spins must be paired.

Write electron configurations for the first 10 elements. Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

Electron Configurations Practice Write the electron configurations for Al Cl

Electron Configurations Practice Write the electron configurations for Al Al 1s2 2s2 2p6 3s2 3p1 Cl Cl 1s2 2s2 p6 3s2 p5

Look in Your Book! Red book pg. 28